Flood-Frequency Analyses Manual of Hydrology: Part 3 Flood Flow Techniques

Abstract

This report describes the method used by the U.S. Geological Survey to determine the magnitude and frequency of momentary peak discharges at any place on a stream, whether a gaging-station record is available or not. The method is applicable to a region of any size, as a river basin or a State, so long as the region is hydrologically homogeneous. The analysis provides two curves. The first expresses the flood discharge time relation, showing variation of peak discharge, expressed as a ratio to the mean annual flood, with recurrence interval. The second relates the mean annual flood to the size of drainage area alone, or to the size area and other significant basin characteristics.